High tension insulator



May 17,- 1932. s. BARFOED HIGH TENSION INSULATOR Filed Feb. 11, 1931INVENTOR.

4 W Y W ATTORNEYS.

Patented May 17, 1932 UNITED- STATES PATENT OFFICE SVEND BARFOED. OF SANFRANCISCO, GALIFORNIA.

HIGH TEN$ION INSULATOR Application filed February ll, 1931. Serial No.514,977.

This invention relates to high tension inunits are made equally able towithstand this sulators and especially to improvements maximum stress. Ithereon whereby the formation of corona In actual practice l haveobserved that if streamers and incipient sparking between the shape ofthe insulators and the contami- S the flanges of an insulator or betweenadjanating layer deposited thereon is such that 50 cent insulators whenmounted in a string is the air becomes overstressed, corona andinmaterially reduced and in many instances encipient sparking willoccur. This takes tirely eliminated. place at sharply rounded edges andtends to The improvement is particularly intended premature sparkoverbetween flanges and befor application to the structure shown in my tweenunit and unit. 55 issued Patent No. 1,742,628, entitled High Thephenomena of corona and incipient tension insulator, issued January 7th,1930, sparking of insulators in foggy weather is but the improvement isalso applicable to frequently referred to as frying and often inothertypes of insulators as will hereinafter creases to undesirable noisesand causing appear. severe interference with radio reception. 1 m

The insulator described in the above menhave observed that the coronastreamers and tioned patent is designed for use in districts incipientsparking heat up the surface of the with a contaminated atmospherecontaining insulating body and the contaminating layer dust, dirt andsalts, etc., in combination with in a multiple of streaks and spotswhereby fog, dew, mist and light rains. These conafter some time thecontaminating layer be- $5 ditions cause a deposit to be formed on thecomes burned or baked on the surface of the surface of the insulatorswhich will be parinsulating body and when this takes place it tiallyconducting to an extent which will pen is very difficult and costly toremove eventumit considerable leakage current to flow. ally alsoinjuring the glaze, which again will This partially conducting layerwill be of the make dirt adhere more easily; the final result an sameshape as the surface of the insulators being that the insulator becomesunsuitable and presents an extension of comparatively for its purposedue to thedestroyed surface high resistance of the metal electrodes andit insulation. will assume a potential corresponding t the AS t s t ofpns derable r s arch and voltage drop along this. If the conditioneXPeI1menl5a1WWkhaVe Q l that comma 3% of the contaminating deposit isuniform and lnclplent p w s: can be p throughout a string of insulatorsthe flow of presse by sllltably P p g the leakage current will cause auniform potent OI mundmg curvature on any P of tial gradient to beestablished along the flanges? Skmts? @rrugatlons and e(lges of stringand the electrical stress with respect is %g i g f th t m to the airwill be a maximum at the line end lee 0 e pnlsen mven Ion 1s m of thestrin and a minimum at the round general y lmpmve and-slmphfy end.Should on the other hand the condihon and operaimon of hlgh t-enslonmSulatO-rs;

f th d b f th th to provlde an lnsulator having a body portion Jon eeposl e nonmm en 9 andaplurality of projecting annular flanges"potential drop along the surface Wlll be nonto provide an insulatorwhich is adapted to llnlforlln and n lay even. from Unit to unit used orin string formation and Parmaxlmum Value and @l Stresses 9 ticularly toround or curve the outer edges of 1mum value on any unit 1n any pos1t1on1n the flanges and the ends of the insulators 45 the string. It istherefore essential that all to such a degree as to-establish a fieldbetween adjacent flanges and units which will not be overstressed orbreak down the insulating value of the surrounding air therebypreventing the formation of corona streamers and incipient sparkingbetween adjacent flanges and units.

The invention is shown by Way of illustration in the accompanyingdrawings, in which- Fig. 1 is an enlarged central, vertical sectionthrough one form of the insulator.

Fig. 2 shows a string or assembly of insulators and a conductorsuspended therefrom.

Fig. 3 shows a standard form of insulator modified or improved accordingto the present invention.

Referring to the drawings in detail and particularly Figs. 1 and 2. Aindicates the cross-arm of a transmission line tower orv pole-ofsuitable construction; B the conductor carrying the high tension currentand C a string of insulators from which the conductor is suspended. Thetype of insulator employed is that illustrated in Fig. 1. It consists ofa head portion 2 and a Petticoat or skirt portion 3. This skirt portionis slightly flared or bell-shaped and its exterior surface is providedwith a suitable number of superposed interspaced annular flan es orpetticoats 4. These petticoats are of substantially equal diameter andan exterior corrugated cylindrical surface is the apparent result. 1

The head member 2 is hollow to receive an anchor bolt 5 which is securedby a cementitious material as indicated at 6. The anchor bolt carries alink 7 and this is, in turn, connected with a metallic h iad member 2awhich encloses the head 2 of the insulator and is secured thereto by acementitious material 8, or the like. The connections bet-ween the headmembers 2a and the anchor bolts 5 are preferably pivotal, as indicatedat 9, and a flexible string of insulators is obtained.

The method of anchoring the bolts 5, the head members 2a and the mannerof attaching the link 7 is of no importance and may be changed to suitvarying conditions.

The manner of forming or shaping the annular flanges and the lower orouter edges of the insulators is of great importance and forms thesubject matter of the present aplication. As previously stated theinvention 1S based on the discovery that the formation of corona andincipient sparking between flanges and units may be materially reducedand in many instances entirely eliminated when the outer contour of theflanges and edges are pro erly formed.

To clearly illustrate and describe this feature reference will be madeto Fig. 1. In this figure it will be noted that the lower end of theinsulator and the annular flanges 4 are decidedly enlarged and roundedas indicated at 10 to provide an exterior curved Voltage to at die-a...line end of vamre string Inches 127, 000 0. 50 116, 000 0. 45 101, 0000. 40 86, 500 0. 32 63, 500 0. B

When an insulator was constructed on this basis it was discovered thatthe resulting wellrounded bulb-shaped flanges and skirts were underadverse conditions able to effect a great improvement in theelectrostatic field surrounding and penetrating any part of theinsulating bodies on the string as a whole, avoiding undesirableconcentration of the electrostatic tubes of force and thereby reducingrefraction where they pass from one medium into another. This result isof great benefit when a transmission line is exposed to lightning.storms.

The usual disc-shaped suspension insulator shown in Fig. 3 and usedalmost universally on high-voltage lines has on its underside severalthin concentric corrugations or skirts with sharply rounded edges asindi' cated by dotted lines at 11 and 12 which during lightning stormsproject into the high-intensity electrostatic field between lineconductor and ground, causing severe refraction of the electrostaticlines of force at the sharply rounded edges. This intensifies theformation of corona-streamers at comparatively low voltage surges andcauses premature sparkover between the insulators. On the other handwhen the outer edge 13 and the corrugations 14 are enlarged and roundedas indicated in full lines in Fig. 3 a great improvement will be found.

In the insulator of the present invention it becomes possible to producelarge units each absorbing a greater proportion of the total voltage.This results in fewer units in a string for a given voltage whereby thevoltage distribution between the units will be improved. The large unitcan be produced on account of the improved electrostatic field madepossible by the grading action in each unit of the well roundedbulb-shaped flanges arranged in the main electrostatic field. Thisaction of the bulb-shaped flanges is similar to the action of shields orrings or other forms of antennae placed at the line end of a string ofinsulators in accordance with usual practice.

In insulators designed in accordance with the resent invention, thedesired result is obtained by the rounded bulb-shaped flanges preyentingpremature breakdown of the air in contact with the surface of theinsulating body during voltage sur es.

It is to be understoo that the radius of curvature selected for eachkind of benefit secured may be the dominating one depending upon theexposure of the transmission line to atmospheric influences of variousdegrees of'severity.

By these means corona. and incipient sparkin can be controlled andsuppressed and a aking and burning on of the contaminating layer on thesurface of the insulators prevented. Undesirable noises and radiointerference will be revented, and finally the insulating value 0 theinsulators can be maintained in an eflicient state by the cleansingaction of the natural rain, as the insulating surface will not bedestroyed.

While certain features of the present invention are more or less s'ifically described, I wish it understoo that various changes may beresorted to within the sco of the appended claims. Similarly that thismaterials and finish of the several parts emloyed may be such as themanufacturer may ecide, or varying conditions or uses may demand.

Having thus described my invention, what I claim and desire to secure byLetters Patent is 1. An insulator having a bod portion, a plurality ofprojecting annu ar flanges ormed thereon, the outer edge of said flangesbeing enlar ed and rounded to such a degree as to estab 'sh a fieldbetween adjacent flanges which will not be overstressed to break downthe insulating value of the surrounding air when subject to highpotential surges.

2. An insulator having a bell-shaped body portion, a plurality ofinterspaced annular flanges formed on the exterior surface of the bodyportion and extending from end to end thereof, the outer ed enlarged androunde to such a degree as to establish a field between adjacent flangeswhich will not be overstressed to break down of said flanges being Iwhen sub'ect to high voltages, the lowermost of said anges beingenlarged to present a largerdegree of curvature than the other flanges.

4. An insulator having a bell-shaped body portion, a plurality ofmterspaced annular anges formed on the exterior surface of the bodyportion and extending from end to end thereof, the outer edge of saidflanges being enlar ed and rounded to such a degree as to estab ish afield between adjacent flanges which will not be overstressed to breakdown the insulating value of the surrounding air when subject to highvoltages, the top and lowermost of said anges being enlarged to presenta larger degree of curvature than the intermediate flan s.

s END BARFOED.

the insulating value of theosurrounding air when subject to highvoltages.

3. An insulator having a bell-sha d body portion, a plurality ofinterspaced innular flanges formed on the exterior surface of the bodyportion and extending from end to end thereof, the outer ed of saidflanges being enlarged and rounde to such a degree as to establish afield between adjacent flanges which will not be overstressed to breakdown the insulating value of the surrounding air

